The ultimate objective of this study is to gain an understanding of the beginning of elevated blood pressure well enough in advance of clinical manifestations to develop a risk factor profile early in life. Specifically, we will explore the relation of the responsiveness of neonates to salt taste stimuli (as a possible correlate of sodium sensitivity) to blood pressures in infancy and early childhood also we will relate these variables to urinary concentrations of sodium, potassium and kallikrein (an enzyme we have shown to be inversely related to blood pressure in older children). These variables might be predictive of later blood pressures. We will also explore the relation of amniotic fluid sodium concentration in the development of neonatal salt taste perception. Our preliminary studies have demonstrated the feasibility of measuring salt taste responsiveness in the newborn and we have shown epidemiologically that elevated neonatal blood pressures are related to higher blood pressures later in infancy. We also have shown that urinary sodium is related to blood pressure in the newborn. Normal newborns will be studied for salt taste responsiveness by analysis of the sucking patterns, heart rate, respiration and movement while the infant receives, via a nipple, tiny drops of water containing two different concentrations of sodium. These responses will be correlated with the electrolytes in urine, saliva and in amniotic fluid and with infants' blood pressure and urinary kallikrein concentration. Since salt intake may be related to the development of essential hypertension in susceptible human populations, an examination of the development of salt taste in the human infant with consideration of the adaptation to amniotic fluid sodium concentration and other environmental influences might have important implications in the genesis of elevated blood pressure. Blood pressure and urinary variables will be studied over a 3-5 year follow-up period.